fix: avoid region fallback panic paths (#2006)

rustfs/src/app/bucket_usecase.rs

@@ -72,13 +72,11 @@ fn to_internal_error(err: impl Display) -> S3Error {
     S3Error::with_message(S3ErrorCode::InternalError, format!("{err}"))
 }
 
-fn default_region() -> Region {
-    // RUSTFS_REGION is a compile-time constant ("us-east-1") guaranteed to be valid.
-    Region::new(RUSTFS_REGION.into()).expect("RUSTFS_REGION constant must be a valid region")
-}
-
-fn resolve_notification_region(global_region: Option<Region>, request_region: Option<Region>) -> Region {
-    global_region.or(request_region).unwrap_or_else(default_region)
+fn resolve_notification_region(global_region: Option<Region>, request_region: Option<Region>) -> String {
+    global_region
+        .or(request_region)
+        .map(|region| region.to_string())
+        .unwrap_or_else(|| RUSTFS_REGION.to_string())
 }
 
 const ERR_LIFECYCLE_RULE_STATUS: &str = "Rule status must be either Enabled or Disabled";
@@ -1218,9 +1216,8 @@ impl DefaultBucketUsecase {
         let event_rules =
             event_rules_result.map_err(|e| s3_error!(InvalidArgument, "Invalid ARN in notification configuration: {e}"))?;
         warn!("notify event rules: {:?}", &event_rules);
-        let region_clone = region.clone();
         notify
-            .add_event_specific_rules(&bucket, region_clone.as_str(), &event_rules)
+            .add_event_specific_rules(&bucket, region.as_str(), &event_rules)
             .await
             .map_err(|e| s3_error!(InternalError, "Failed to add rules: {e}"))?;
 
@@ -1758,22 +1755,19 @@ mod tests {
     #[test]
     fn resolve_notification_region_prefers_global_region() {
         let binding = resolve_notification_region(Some("us-east-1".parse().unwrap()), Some("ap-southeast-1".parse().unwrap()));
-        let region = binding.as_str();
-        assert_eq!(region, "us-east-1");
+        assert_eq!(binding, "us-east-1");
     }
 
     #[test]
     fn resolve_notification_region_falls_back_to_request_region() {
         let binding = resolve_notification_region(None, Some("ap-southeast-1".parse().unwrap()));
-        let region = binding.as_str();
-        assert_eq!(region, "ap-southeast-1");
+        assert_eq!(binding, "ap-southeast-1");
     }
 
     #[test]
     fn resolve_notification_region_defaults_value() {
         let binding = resolve_notification_region(None, None);
-        let region = binding.as_str();
-        assert_eq!(region, RUSTFS_REGION);
+        assert_eq!(binding, RUSTFS_REGION);
     }
 
     #[tokio::test]

rustfs/src/app/multipart_usecase.rs

@@ -79,7 +79,7 @@ impl DefaultMultipartUsecase {
         self.context.as_ref().and_then(|context| context.bucket_metadata().handle())
     }
 
-    fn global_region(&self) -> Option<s3s::region::Region> {
+    fn global_region(&self) -> Option<Region> {
         self.context.as_ref().and_then(|context| context.region().get())
     }
 
@@ -339,12 +339,13 @@ impl DefaultMultipartUsecase {
 
         let region = self
             .global_region()
-            .unwrap_or_else(|| Region::new(RUSTFS_REGION.into()).expect("RUSTFS_REGION constant must be a valid region"));
+            .map(|region| region.to_string())
+            .unwrap_or_else(|| RUSTFS_REGION.to_string());
         let output = CompleteMultipartUploadOutput {
             bucket: Some(bucket.clone()),
             key: Some(key.clone()),
             e_tag: obj_info.etag.clone().map(|etag| to_s3s_etag(&etag)),
-            location: Some(region.to_string()),
+            location: Some(region.clone()),
             server_side_encryption: server_side_encryption.clone(),
             ssekms_key_id: ssekms_key_id.clone(),
             checksum_crc32: checksum_crc32.clone(),
@@ -356,16 +357,11 @@ impl DefaultMultipartUsecase {
             version_id: mpu_version,
             ..Default::default()
         };
-        info!(
-            "TDD: Created output: SSE={:?}, KMS={:?}",
-            output.server_side_encryption, output.ssekms_key_id
-        );
-
         let helper_output = entity::CompleteMultipartUploadOutput {
             bucket: Some(bucket.clone()),
             key: Some(key.clone()),
             e_tag: obj_info.etag.clone().map(|etag| to_s3s_etag(&etag)),
-            location: Some(region.to_string()),
+            location: Some(region),
             server_side_encryption,
             ssekms_key_id,
             checksum_crc32,
@@ -376,6 +372,10 @@ impl DefaultMultipartUsecase {
             checksum_type,
             ..Default::default()
         };
+        info!(
+            "TDD: Created output: SSE={:?}, KMS={:?}",
+            output.server_side_encryption, output.ssekms_key_id
+        );
 
         let mt2 = HashMap::new();
         let replicate_options =